1. Field of Invention
This invention relates to the generation of electricity from human movement.
2. Background and Related Art
With the proliferation of mobile electrical devices, there is increasing need for better methods of providing electrical power to these devices. This need has prompted a stream of research that focuses on alternative methods of mobile power generation, including methods of generating electricity from movement of the human body.
General approaches to generating electricity from movement of the human body include: (1) interaction of a human with an external piece of equipment; (2) footwear that converts energy from walking into electricity; (3) wearable fabric with electrochemical structures or reactions to convert energy from human movement into electricity; (4) gravity-based kinetic energy harvesting devices; and (5) other kinetic energy harvesting devices. Some of these approaches, such as shoe-based approaches, are well developed in the related art. Others are not yet well developed. All of the current methods based on these approaches have disadvantages.
(1) Interaction of a Human with an External Piece of Equipment
Interaction of humans with external equipment can involve humans using exercise and playground equipment, pulling levers and turning cranks, carrying backpacks, and using other methods. Such methods for generating electricity from human movement are disclosed by U.S. Pat. No. 5,358,461 (Bailey), U.S. Pat. No. 6,293,771 (Haney), U.S. Pat. No. 6,982,497 (Rome), U.S. Pat. No. 7,005,757 (Pandian), U.S. Pat. No. 7,129,592 (Yetter), U.S. Pat. No. 7,361,999 (Yeh), U.S. Pat. No. 7,391,123 (Rome), and applications 20040183306 (Rome) and 20060192386 (Rome). Disadvantages of this general approach include: methods with significant size equipment are not portable; those that require specific actions by body members (such as hand pulling) do not leave those members free for other activities; and it is difficult to harvest energy from a large portion of body movement without a large, cumbersome piece of equipment.
(2) Footwear that Converts Energy from Walking into Electricity
There are many examples of shoes in the related art that convert contact energy from walking or running into electricity. These examples include U.S. Pat. No. 1,506,282 (Barbieri), U.S. Pat. No. 5,167,082 (Chen), U.S. Pat. No. 5,495,682 (Chen), U.S. Pat. No. 6,182,378 (Sendaula), U.S. Pat. No. 6,201,314 (Landry), U.S. Pat. No. 6,239,501 (Komarechka), U.S. Pat. No. 6,255,799 (Le), U.S. Pat. No. 6,281,594 (Sarich), U.S. Pat. No. 6,744,145 (Chang), U.S. Pat. No. 7,327,046 (Biamonte), and application 20070145746 (Biamonte). Disadvantages of shoes that convert energy from walking into electricity include: such shoes do not capture energy from upper legs or the entire rest of the body; shoes that harvest energy from contact with a support surface do not work in zero-gravity environments or low-contact environments such as water; and shoes with moving elements on the sole may interfere with balance and traction.
(3) Wearable Fabric with Electrochemical Structures or Reactions
Some approaches to generating electricity from human body movement use electrochemical structures or reactions, such as piezoelectric or hydrogen-based generators. Examples of such approaches in the related art include U.S. Pat. No. 6,433,465 (McKnight), U.S. Pat. No. 6,709,778 (Johnson), U.S. Pat. No. 6,737,789 (Radziemski), U.S. Pat. No. 7,081,699 (Keolian), U.S. Pat. No. 7,304,416 (Mullen), U.S. Pat. No. 7,249,805 (Cap), and application 20050255349 (Fisher). Disadvantages of using electrochemical methods such as these include: to date they create very small amounts of electricity; and many of the electrochemical structures are not washable.
(4) Gravity-Based Kinetic Energy Harvesting Devices
Some approaches to generating electricity from human body movement harvest kinetic energy through the force of gravity on a moving object. For example, a cell phone carried by a human often moves around and a free-moving member within that phone will move relative to the phone due to the pull of gravity. This relative motion can be harvested into electricity to power the phone. U.S. Pat. No. 6,316,906 (Lozada) and U.S. Pat. No. 7,266,396 (Terzian) disclose such approaches. Disadvantages of this approach include: they harvest relatively small amounts of energy; and it is difficult to use such approaches to capture energy from large portions of the human body.
(5) Other Kinetic Energy Harvesting Devices
The related art also includes non-gravity-based approaches to converting kinetic energy from human movement into electricity. For example, methods that convert the pulsing action of a blood vessel into electricity are disclosed in U.S. Pat. No. 5,431,694 (Snaper), U.S. Pat. No. 7,081,683 (Ariav), and application 20070167988 (Cernasov). Converting energy from blood vessel pulsation is limited in terms of the amount of electricity and is limited in external applications by the proximity of blood vessels to the body surface. Another interesting invention involving harvesting energy is U.S. Pat. No. 7,233,829 (Vlad) which discloses a shark-repelling wet suit with an electric field.
U.S. Pat. No. 6,822,343 (Estevez) and application 20030168861 (Estevez) disclose a device for obtaining electricity from fluid flow between an inner passage closer to the body and outer passage farther from the body. A major disadvantage of this approach is that body movement, such as the knee bending, will bend and pressurize both the inner and outer passages, so the pressure differential between inner and outer passages is much less than the pressure differential between two sequential passages along the body surface, one in the area being bent and the other in a non-bending area. With overlapping inner and outer passages, much of the energy from bending is not captured. Another disadvantage of overlapping inner and outer passages is the resulting double thickness. Double thickness can be cumbersome when one is striving to make an electricity-generating garment as unobtrusive as possible. As another disadvantage, when a generator is sandwiched between an inner and outer layer, it is not easy to remove and replace the generator so that the garment can be washed.
(6) Summary of the Background and Related Art
Although there has been a good deal of creative work toward generating electricity from human movement, the current methods all have disadvantages. There remains a need for a wearable, portable, washable, and relatively unobtrusive device that can efficiently convert movement of a relatively large portion of the human body into electricity. That is what this present invention does.